1. Field of the Invention
This invention relates to improvements in an airbag arrangement for protecting a vehicle passenger in the event of a serious vehicle collision, and more particularly to an airbag having an inner surface coated with an elastomeric material to prevent gas from penetrating it.
2. Description of the Prior Art
A variety of airbag arrangements for an automotive vehicle have been proposed and put into practical use. A typical arrangement is configured as follows. An airbag is usually folded and retracted in a central part of a steering wheel and covered with a pad. The airbag is arranged burst the pad to open and to thereby protect a vehicle passenger from coming into direct contact with either the steering wheel or a windshield in the event of a serious vehicle collision. The airbag is made up of front and rear generally annular sheets (woven cloths) which are sewn at their peripheral portion to each other. The rear sheet is formed with a central opening for receiving an inflator or gas generator which ejects nitrogen gas. The front and rear sheets are coated at their inner surface with an elastomeric material to prevent the gas from passing therethrough. Accordingly, the airbag can be inflated when the inflator generates the gas. The rear sheet is formed with gas discharge openings through which a part of the gas inside the airbag is discharged so that the airbag serves as a soft cushion, thereby protecting the passenger.
However, difficulties have been encountered in such a conventional airbag arrangement in which it is necessary to particularly reinforce the inner peripheral portion of the rear sheet around each gas discharge opening in order to prevent the rear sheet from tearing from the gas discharge openings when the gas is forcibly discharged through the gas discharge openings. This increases the number of steps in the production process and raises production costs.
In view of the above, it may be proposed to leave an uncoated section (having no coating) at a part of the rear sheet so as to allow a part of the gas inside the airbag to be discharged. However, it is difficult to determine a suitable location for the uncoated section. In other words, if the uncoated section is formed at an unsuitable location, the gas inside the airbag will be excessively discharged so that the airbag cannot be sufficiently inflated, or the discharge of the gas will be insufficient so that the airbag will not serve as a soft cushion.